Turnbull, of Strule Park, Omagh, Co Tyrone, also pleaded guilty to further counts on the same date of possessing a Sterling submachine gun and ammunition with intent along with articles likely to be used in terrorism.

Mark McGuigan, 29, of Sperrin View, Omagh, was found guilty at his trial last November of possessing a firearm with intent.

The four were caught in a Ford Fiesta car on October 11, 2010 on the Gorticashel Road outside Omagh, Co Tyrone.

In a green Celtic holdall police found a reactivated . 38 Webley revolver hidden in a sock.

Belfast Crown Court had earlier heard that inside a second sock was a quantity of ammunition, including 13 rounds of .22 rimfire rifle cartridges and 20 rounds of 9 x 19 mm calibre cartridges.

Judge Corinne Philpott QC sentenced McGuigan to 12 years, with six years in custody and a further six on licence.

The judge said: “McGuigan still denies responsibility for his actions. He has shown no remorse and does not regret his involvement.”

The court heard that Turnbull had now “seen the error of his ways’’ and was no longer part of the dissident republican wings in Maghaberry prison.

Judge Philpott sentenced Turnbull to nine years, with four-and-a-half years in custody and the remainder on licence.

The court had heard that the day after their arrests on October 12, police carried out a search at 5 Mill Cottages in Greencastle, Co Tyrone, and found a Renault Clio car belonging to Turnbull parked outside. Inside the car, officers found a submachine gun and magazine along with 42 .22 calibre cartridges.

The search of the car also uncovered three sets of ballistic body armour, latex gloves, ear defenders and combat clothing.

McLoone, whose DNA was found on a Celtic bag, was sentenced to eight years, with an equal 50/50 split between custody and licence. McCallion was sentenced to seven years, with three-and-a-half years in custody and the remainder on licence on his release.